Java Today

Software Support & Development for Students, Shops and Companies

2016-09-15T01:34:00.000-04:00

All types of Software Applications and Android Apps can be developed and designed:

1. Student's Vacation software projects
2. Management related software
3. Billing Softwares
4. Inventory related softwares
5. College software projects
and many more....

Spring and RESTful webservice Integration

2016-07-05T07:06:00.002-04:00

Spring and RESTful webservice Integration

Earlier, we had developed an application using Spring and Rest. But, this is a basic app which shows integration of Spring with Rest at a beginner level. This demo app is for freshers.

Following below steps to create this application:

1) Libraries required:

spring-core 4.1.6 RELEASE

spring-web 4.1.6 RELEASE

spring-webmvc 4.1.6 RELEASE

jstl 1.2

2) Create a xml file named as web.xml in WEB-INF folder and write following code:

<!DOCTYPE web-app PUBLIC

"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"

"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>

<display-name>Archetype Created Web Application</display-name>

<servlet-name>springrest</servlet-name>

<servlet-class>

org.springframework.web.servlet.DispatcherServlet

</servlet-class>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>springrest</servlet-name>

<url-pattern>/</url-pattern>

</servlet-mapping>

</web-app>

3) Create a xml file named as springrest-servlet.xml in WEB-INF folder and write following code in it:

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:context="http://www.springframework.org/schema/context"

xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context

http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

<mvc:annotation-driven />

<context:component-scan base-package="com.gag.controller" />

</beans>

4) Create a package named as com.gag.controller and Create a class named as SpringRestController.java and write following code in it:

package com.gag.controller;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.RestController;

@RestController

@RequestMapping("/hello")

public class SpringRestController {

@RequestMapping(value = "/{name}", method = RequestMethod.GET)

public String hello(@PathVariable String name) {

String result = "Hello " + name;

return result;

}

5) Create a JSP or any html file and write following code in it:

<html>

<body>

<a href="hello/Gagan">Say Hello</a>

</body>

</html>

Our output would be like as below:

This is an anchor tag on which you would click and a Hello Message is shown:

RESTful webservice along with Spring 4 and AngularJS

2016-06-29T05:59:00.002-04:00

In our earlier post, we developed a small application using REST and AngularJS. Follow this link for help http://techs4.blogspot.in/2016/06/restful-webservice-using-jersey.html Now, we are going to use Spring 4 to handle REST as it is used now a days in most IT-Software projects.

We would be using Spring Controller to handle REST request/response. In Spring 4, there is a new concept of @RestController Annotation.

Overview of our application:

Our front-end would look like as below:

Follow below steps to create this small application:

a) Libraries required:

jersey-server 1.9
mysql-connector-java 5.1.10
com.google.code.gson (gson) 2.2.1
spring-core 4.1.6
spring-web 4.1.6
spring-webmvc 4.1.6
javax.servlet-api 3.1.0

b) Create a xml file named as spring-servlet.xml in WEB-INF folder and write following code in it:

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:mvc="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

<mvc:annotation-driven />
<context:component-scan base-package="com.gag" />

</beans>

c) Create another xml file named as web.xml in WEB-INF folder and write following code in it:

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
</web-app>

d) Create a properties file named as configuration.properties and write following code in it:

jdbc.driver = com.mysql.jdbc.Driver

jdbc.url = jdbc:mysql:///um

jdbc.user = root

e) Create a package named as com.gag and within this package Create a class (POJO) named as Customer.java in it:

package com.gag;

public class Customer {

private Integer id;

private String name, email;

public String getName() {

return name;

}

public Integer getId() {

return id;

}

public void setId(Integer id) {

this.id = id;

}

public void setName(String name) {

this.name = name;

}

public String getEmail() {

return email;

}

public void setEmail(String email) {

this.email = email;

}

f) Create a class named as ReadFromPropertiesFile.java in which following code is to be written:

package com.gag;

import java.io.InputStream;

import java.util.Properties;

public class ReadFromPropertiesFile {

Properties properties = null;

ReadFromPropertiesFile() {

try {

InputStream is = ReadFromPropertiesFile.class.getClassLoader()

.getResourceAsStream("configuration.properties");

properties = new Properties();

properties.load(is);

} catch (Exception e) {

System.out.println("aaaa " + e);

}

public String getURL() {

try {

return properties.getProperty("jdbc.url");

} catch (Exception e) {

System.out.println("getURL:" + e);

}

return "";

}

g) Create another class named as ConnectDB.java in which database connectivity is performed:

package com.gag;

import java.sql.Connection;

import java.sql.DriverManager;

import java.util.logging.Logger;

public class ConnectDB {

static ReadFromPropertiesFile obj = new ReadFromPropertiesFile();

public static Connection connect() {

Connection conn = null;

try {

Class.forName("com.mysql.jdbc.Driver");

conn = DriverManager.getConnection(obj.getURL(), "root", "");

} catch (Exception e) {

Logger.getLogger(ConnectDB.class + "");

}

return conn;

}

h) Create a service layer class named as CustomerServices.java and write following code in it:

package com.gag;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.util.ArrayList;

import java.util.List;

public class CustomerServices {

public List<Customer> getAllCustomers() {

List<Customer> lst = new ArrayList();

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("select * from customer order by id");

ResultSet rs = pstmt.executeQuery();

while (rs.next()) {

Customer obj = new Customer();

obj.setId(rs.getInt("id"));

obj.setName(rs.getString("name"));

obj.setEmail(rs.getString("email"));

lst.add(obj);

}

} catch (Exception e) {

System.out.println(e);

}

return lst;

}

public String addCustomer(Customer obj) {

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("insert into customer values(?,?,?)");

pstmt.setInt(1, obj.getId());

pstmt.setString(2, obj.getName());

pstmt.setString(3, obj.getEmail());

int i = pstmt.executeUpdate();

if (i > 0) {

return "Customer Created";

}

} catch (Exception e) {

System.out.println("addCustomer: " + e);

}

return "Failed to Create Customer";

}

public String updateCustomer(Customer obj) {

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("update customer set name=?,email = ? where id = ?");

pstmt.setString(1, obj.getName());

pstmt.setString(2, obj.getEmail());

pstmt.setInt(3, obj.getId());

int i = pstmt.executeUpdate();

if (i > 0) {

return "Customer Updated";

}

} catch (Exception e) {

System.out.println("updateCustomer: " + e);

}

return "Failed to Update Customer";

}

public String delCustomer(int id) {

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("delete from customer where id = ?");

pstmt.setInt(1, id);

int i = pstmt.executeUpdate();

if (i > 0) {

return "Customer Deleted";

}

} catch (Exception e) {

System.out.println("delCustomer: " + e);

}

return "Failed to Delete Customer";

}

i) Create a class named as CustomerAPI.java and write following code in it:

package com.gag;

import java.util.List;

import javax.ws.rs.core.MediaType;

import org.springframework.http.HttpStatus;

import org.springframework.http.ResponseEntity;

import org.springframework.web.bind.annotation.PathVariable;

import org.springframework.web.bind.annotation.RequestBody;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.bind.annotation.RequestMethod;

import org.springframework.web.bind.annotation.RestController;

import com.google.gson.Gson;

@RestController

public class CustomerAPI {

@RequestMapping(value = "/getCustomers", method = RequestMethod.GET, produces = "application/json")

public String feed() {

String feeds = null;

try {

List<Customer> lstCustomers = null;

CustomerServices customerServices = new CustomerServices();

lstCustomers = customerServices.getAllCustomers();

Gson gson = new Gson();

feeds = gson.toJson(lstCustomers);

} catch (Exception e) {

System.out.println("Exception Error"); // Console

}

return feeds;

}

@RequestMapping(value = "/addCustomer", method = RequestMethod.POST, consumes = MediaType.APPLICATION_JSON)

public ResponseEntity createCustomer(@RequestBody Customer obj) {

String result = "";

try {

CustomerServices customerServices = new CustomerServices();

result = customerServices.addCustomer(obj);

} catch (Exception e) {

System.out.println("Exception Error " + e); // Console

}

return new ResponseEntity(HttpStatus.CREATED);

}

@RequestMapping(value = "/updateCustomer/id/{id}/name/{name}/email/{email}", method = RequestMethod.PUT)

public ResponseEntity<String> updateCustomer(@PathVariable("id") int id,

@PathVariable("name") String name,

@PathVariable("email") String email) {

String result = "";

try {

CustomerServices customerServices = new CustomerServices();

Customer obj = new Customer();

obj.setId(id);

obj.setName(name);

obj.setEmail(email);

result = customerServices.updateCustomer(obj);

} catch (Exception e) {

System.out.println("Exception Error " + e); // Console

}

return new ResponseEntity<String>(HttpStatus.CREATED);

}

@RequestMapping(value = "/delCustomer/id/{id}", method = RequestMethod.DELETE)

public ResponseEntity<String> delCustomer(@PathVariable("id") Integer id) {

if (id > 0) {

String result = "";

System.out.println("Id:: " + id);

try {

CustomerServices customerServices = new CustomerServices();

result = customerServices.delCustomer(id);

} catch (Exception e) {

System.out.println("Exception Error " + e); // Console

}

return new ResponseEntity<String>(HttpStatus.CREATED);

} else {

return new ResponseEntity<String>(HttpStatus.NOT_ACCEPTABLE);

}

j) Create an index.jsp file and write following code in it:

<html>

<head>

href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">

<script

src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>

<script

src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.4/angular.js"></script>

var myapp = angular.module("myApp", []);

myapp.controller("umcontroller", function($scope, $http) {

$scope.employees = [];

$scope.form = {

id : "",

name : "",

email : ""

};

_refreshPageData();

$scope.check = "";

$scope.submitCustomer = function() {

if ($scope.form.check == "check") {

method = "PUT";

url = 'updateCustomer/id/' + $scope.form.id + "/name/"

+ $scope.form.name + "/email/" + $scope.form.email;

} else {

method = "POST";

url = 'addCustomer';

}

$http({

method : method,

url : url,

data : angular.toJson($scope.form),

headers : {

'Content-Type' : 'application/json'

}

}).then(function successCallback(response) {

$scope.form.check = "";

_success(response);

});

};

$scope.removeEmployee = function(employee) {

$http({

method : 'DELETE',

url : 'delCustomer/id/' + employee.id

}).then(function successCallback(response) {

_success(response);

});

};

$scope.editEmployee = function(employee) {

$scope.form.name = employee.name;

$scope.form.email = employee.email;

$scope.form.id = employee.id;

$scope.form.check = "check";

};

function _refreshPageData() {

$http({

method : 'GET',

url : 'getCustomers'

}).then(function successCallback(response) {

$scope.employees = response.data;

}, function errorCallback(response) {

console.log(response.statusText);

});

}

function _success(response) {

_refreshPageData();

_clearForm()

}

function _error(response) {

console.log(response.statusText);

}

function _clearForm() {

$scope.form.name = "";

$scope.form.email = "";

$scope.form.id = "";

}

$scope.clearForm = function() {

_clearForm();

}

});

</script>

</head>

<span class="lead">User Registration Form </span>

</div>

<input type="hidden" ng-model="form.id" /> <input type="hidden"

ng-model="form.check" />

<input type="text" ng-model="form.id" name="id"

class="username form-control input-sm"

placeholder="Enter your Id" required ng-minlength="1" />

</div>

<input type="text" ng-model="form.name" id="name"

class="username form-control input-sm"

placeholder="Enter your name" required ng-minlength="3" />

</div>

<label class="col-md-2 control-lable" for="email">Email</label>

<input type="text" ng-model="form.email" id="email" name="email"

class="form-control input-sm"

placeholder="Enter your Email [This field is validation free]" />

</div>

<input type="submit" value="{{!form.check ? 'Add' : 'Update'}}"

class="btn-sm" ng-disabled="myForm.$invalid">

<button type="button" ng-click="clearForm()"

class="btn-sm">Reset Form</button>

</div>

</form>

</div>

<span class="lead">List of Users </span>

</div>

<thead>

<tr>

<th>Email</th>

</tr>

</thead>

<tbody>

<td>

<button type="button" ng-click="editEmployee(u)"

class="btn btn-success custom-width">Edit</button>

<button type="button" ng-click="removeEmployee(u)"

class="btn btn-danger custom-width">Remove</button>

</td>

</tr>

</tbody>

</table>

</div>

</body>

</html>

RESTful WebService using Jersey, AngularJS, MySQL (Small application to maintain users - Usermaintenance)

2016-06-23T05:58:00.001-04:00

RESTful WebService using Jersey, AngularJS, MySQL

In this application, we will use AngularJS at the front-end and MySQL at the back-end. Moreover, Angular will communicate with database to store and fetch information using RESTful webservices. Obviously, we would be using JSON format for transfer of data from angular to rest and vice versa.

Following some steps to achieve this task and our output will be as below:

a) Libraries required:

jersey-server 1.9

mysql-connector-java 5.1.10

(com.google.code.gson) gson 2.2.1

b) Create a property file named as configuration.properties and write following lines:

jdbc.driver = com.mysql.jdbc.Driver

jdbc.url = jdbc:mysql:///um

jdbc.user = root

c) Create a package named as com.gag and Create a class named as ReadFromPropertiesFile.java and write following lines in it:

package com.gag;

import java.io.InputStream;

import java.util.Properties;

public class ReadFromPropertiesFile {

Properties properties = null;

ReadFromPropertiesFile() {

try {

InputStream is = ReadFromPropertiesFile.class.getClassLoader()

.getResourceAsStream("configuration.properties");

properties = new Properties();

properties.load(is);

} catch (Exception e) {

System.out.println("aaaa " + e);

}

public String getURL() {

try {

return properties.getProperty("jdbc.url");

} catch (Exception e) {

System.out.println("getURL:" + e);

}

return "";

}

d) Create a class named as ConnectDB.java and write following lines in it:

package com.gag;

import java.sql.Connection;

import java.sql.DriverManager;

import java.util.logging.Logger;

public class ConnectDB {

static ReadFromPropertiesFile obj = new ReadFromPropertiesFile();

public static Connection connect() {

Connection conn = null;

try {

Class.forName("com.mysql.jdbc.Driver");

conn = DriverManager.getConnection(obj.getURL(), "root", "");

} catch (Exception e) {

System.out.println("ConnectDB: " + e);

Logger.getLogger(ConnectDB.class + "");

}

return conn;

}

e) Create a POJO class named as Customer.java and write following lines in it:

package com.gag;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement

public class Customer {

private int id;

private String name, email;

public int getId() {

return id;

}

public void setId(int id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getEmail() {

return email;

}

public void setEmail(String email) {

this.email = email;

}

@Override

public String toString() {

return "{\"id\":\"" + id + "\",\"name\":\"" + name + "\",\"email\":\""

+ email + "\"}";

}

f) Create a class CustomerServices.java and write following lines in it:

package com.gag;

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.util.ArrayList;

import java.util.List;

public class CustomerServices {

public List<Customer> getAllCustomers() {

List<Customer> lst = new ArrayList();

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("select * from customer");

ResultSet rs = pstmt.executeQuery();

while (rs.next()) {

Customer obj = new Customer();

obj.setId(rs.getInt("id"));

obj.setName(rs.getString("name"));

obj.setEmail(rs.getString("email"));

lst.add(obj);

}

} catch (Exception e) {

System.out.println(e);

}

return lst;

}

public String addCustomer(Customer obj) {

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("insert into customer values(?,?,?)");

pstmt.setInt(1, obj.getId());

pstmt.setString(2, obj.getName());

pstmt.setString(3, obj.getEmail());

int i = pstmt.executeUpdate();

if (i > 0) {

return "{\"msg\":\"Customer Created\"}";

}

} catch (Exception e) {

System.out.println("addCustomer: " + e);

}

return "{\"msg\":\"Failed to Create Customer\"}";

}

public String updateCustomer(Customer obj) {

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("update customer set name=?,email = ? where id = ?");

pstmt.setString(1, obj.getName());

pstmt.setString(2, obj.getEmail());

pstmt.setInt(3, obj.getId());

int i = pstmt.executeUpdate();

if (i > 0) {

return "{\"msg\":\"Customer Updated\"}";

}

} catch (Exception e) {

System.out.println("updateCustomer: " + e);

}

return "Failed to Update Customer";

}

public String delCustomer(int id) {

try {

Connection conn = ConnectDB.connect();

PreparedStatement pstmt = conn

.prepareStatement("delete from customer where id = ?");

pstmt.setInt(1, id);

int i = pstmt.executeUpdate();

if (i > 0) {

return "{\"msg\":\"Customer Deleted\"}";

}

} catch (Exception e) {

System.out.println("delCustomer: " + e);

}

return "Failed to Delete Customer";

}

g) Create a class named as CustomerAPI.java in which we will write our RESTful webservice code:

package com.gag;

import java.util.List;

import javax.ws.rs.DELETE;

import javax.ws.rs.GET;

import javax.ws.rs.POST;

import javax.ws.rs.PUT;

import javax.ws.rs.Path;

import javax.ws.rs.PathParam;

import javax.ws.rs.Produces;

import javax.ws.rs.core.MediaType;

import javax.ws.rs.core.Response;

import com.google.gson.Gson;

@Path("/customer")

public class CustomerAPI {

@GET

@Path("/getCustomers")

@Produces("application/json")

public String feed() {

String feeds = null;

try {

List<Customer> lstCustomers = null;

CustomerServices customerServices = new CustomerServices();

lstCustomers = customerServices.getAllCustomers();

Gson gson = new Gson();

System.out.println(gson.toJson(lstCustomers));

feeds = gson.toJson(lstCustomers);

} catch (Exception e) {

System.out.println("Exception Error"); // Console

}

return feeds;

}

@POST

@Path("/addCustomer")

@Produces(MediaType.APPLICATION_JSON)

public Response createCustomer(Customer customer) {

System.out.println();

String result = "";

try {

CustomerServices customerServices = new CustomerServices();

result = customerServices.addCustomer(customer);

} catch (Exception e) {

System.out.println("Exception Error " + e); // Console

}

return Response.status(200).entity(result).build();

}

@PUT

@Path("/updateCustomer/id/{id}/name/{name}/email/{email}")

public String updateCustomer(@PathParam("id") int id,

@PathParam("name") String name, @PathParam("email") String email) {

String result = "";

try {

CustomerServices customerServices = new CustomerServices();

Customer obj = new Customer();

obj.setId(id);

obj.setName(name);

obj.setEmail(email);

result = customerServices.updateCustomer(obj);

} catch (Exception e) {

System.out.println("Exception Error " + e); // Console

}

return result;

}

@DELETE

@Path("/delCustomer/id/{id}")

public String delCustomer(@PathParam("id") int id) {

String result = "";

try {

CustomerServices customerServices = new CustomerServices();

result = customerServices.delCustomer(id);

} catch (Exception e) {

System.out.println("Exception Error " + e); // Console

}

return result;

}

h) Create a xml file named as web.xml and write following code in it:

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>jersey-servlet</servlet-name>
<servlet-class>com.sun.jersey.spi.container.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>com.sun.jersey.config.property.packages</param-name>
<param-value>com.gag</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>jersey-servlet</servlet-name>
<url-pattern>/rest/*</url-pattern>
</servlet-mapping>

</web-app>

i) In the last, to use this API, we need a client, so we will use angularjs along with jquery and html. Following is the code in index.jsp file or any html file you can create:

<html>

<head>

href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">

<script

src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>

<script

src="https://ajax.googleapis.com/ajax/libs/angularjs/1.4.4/angular.js"></script>

var myapp = angular.module("myApp", []);

myapp

.controller(

"umcontroller",

function($scope, $http) {

$scope.employees = [];

$scope.form = {

id : "",

name : "",

email : ""

};

_refreshPageData();

$scope.check = "";

$scope.submitCustomer = function() {

if ($scope.form.check == "check") {

method = "PUT";

url = 'http://localhost:8088/CustomerJerseyRestAPI/rest/customer/updateCustomer/id/'

+ $scope.form.id

+ "/name/"

+ $scope.form.name

+ "/email/"

+ $scope.form.email;

} else {

method = "POST";

url = 'http://localhost:8088/CustomerJerseyRestAPI/rest/customer/addCustomer';

}

$http({

method : method,

url : url,

data : angular.toJson($scope.form),

headers : {

'Content-Type' : 'application/json'

}

}).then(function successCallback(response) {

$scope.form.check = "";

_success(response);

}, function errorCallback(response) {

alert("ERROE:: " + response);

});

};

$scope.removeEmployee = function(employee) {

$http(

{

method : 'DELETE',

url : 'http://localhost:8088/CustomerJerseyRestAPI/rest/customer/delCustomer/id/'

+ employee.id

}).then(function successCallback(response) {

_success(response);

}, function errorCallback(response) {

alert("ERROE:: " + response);

});

};

$scope.editEmployee = function(employee) {

$scope.form.name = employee.name;

$scope.form.email = employee.email;

$scope.form.id = employee.id;

$scope.form.check = "check";

};

function _refreshPageData() {

$http(

{

method : 'GET',

url : 'http://localhost:8088/CustomerJerseyRestAPI/rest/customer/getCustomers/'

}).then(function successCallback(response) {

$scope.employees = response.data;

}, function errorCallback(response) {

console.log(response.statusText);

});

}

function _success(response) {

_refreshPageData();

_clearForm()

}

function _error(response) {

console.log(response.statusText);

}

function _clearForm() {

$scope.form.name = "";

$scope.form.email = "";

$scope.form.id = "";

}

$scope.clearForm = function() {

_clearForm();

}

});

</script>

</head>

<span class="lead">Usermaintenance</span>

</div>

<input type="hidden" ng-model="form.id" /> <input type="hidden"

ng-model="form.check" />

<input type="text" ng-model="form.id" name="id"

class="username form-control input-sm"

placeholder="Enter your Id" required ng-minlength="1" />

</div>

<input type="text" ng-model="form.name" id="name"

class="username form-control input-sm"

placeholder="Enter your name" required ng-minlength="3" />

</div>

<label class="col-md-2 control-lable" for="email">Email</label>

<input type="text" ng-model="form.email" id="email" name="email"

class="form-control input-sm"

placeholder="Enter your Email [This field is validation free]" />

</div>

<input type="submit" value="{{!form.check ? 'Add' : 'Update'}}"

class="btn-sm" ng-disabled="myForm.$invalid">

<button type="button" ng-click="clearForm()"

class="btn-sm">Reset Form</button>

</div>

</form>

</div>

<span class="lead">Users</span>

</div>

<thead>

<tr>

<th>Email</th>

</tr>

</thead>

<tbody>

<td>

<button type="button" ng-click="editEmployee(u)"

class="btn btn-success custom-width">Edit</button>

<button type="button" ng-click="removeEmployee(u)"

class="btn btn-danger custom-width">Remove</button>

</td>

</tr>

</tbody>

</table>

</div>

</body>

</html>

Spring MVC Multiple Controller Example

2016-06-22T08:30:00.000-04:00

Spring MVC Multiple Controller Example

a) Libraries to be used:

spring-core - 4.1.6

spring-web - 4.1.6

spring-webmvc - 4.1.6

javax.servlet-api - 3.1.0

jstl - 1.2

b) Create a xml file named as web.xml in WEB-INF folder and write the following code in it:

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>*.html</url-pattern>
</servlet-mapping>

</web-app>

c) Create a xml file named as spring-servlet.xml in WEB-INF folder and write following code in it:

<beans xmlns="http://www.springframework.org/schema/beans"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"

xmlns:context="http://www.springframework.org/schema/context"

xsi:schemaLocation="http://www.springframework.org/schema/beans

http://www.springframework.org/schema/beans/spring-beans-3.0.xsd

http://www.springframework.org/schema/context

http://www.springframework.org/schema/context/spring-context-3.0.xsd">

<context:component-scan base-package="com.gag.controller" />

<bean

class="org.springframework.web.servlet.view.InternalResourceViewResolver">

</bean>

</beans>

d) Create an index.jsp and do following code in it:

<html>

<body>

<h2>Hello World!</h2>

<a href="hello.html">Hello Controller</a>

<a href="welcome.html">Welcome Controller</a>

</body>

</html>

e) Create a folder named jsp in WEB-INF folder and Create following JSP pages in this folder:

data.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

<h1>Hi you have arrived on Hello COntroller.....</h1>

</body>

</html>

and gagandeep.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>

<head>

<title>Insert title here</title>

</head>

<body>

<h1>Hii..you have arrived on Welcome Controller....</h1>

</body>

</html>

e) Create a package named as com.gag.controller and within this package Create following classes in it:

HelloController.java

package com.gag.controller;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.ModelAndView;

@Controller

public class HelloController {

@RequestMapping("/hello")

public ModelAndView helloWorld() {

String message = "HELLO CONTROLLER";

System.out.println("Heloooo..........");

return new ModelAndView("data", "message", message);

}

WelcomeController.java

package com.gag.controller;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestMapping;

import org.springframework.web.servlet.ModelAndView;

@Controller

public class WelcomeController {

@RequestMapping("/welcome")

public ModelAndView helloWorld() {

String message = "WELCOME CONTROLLER";

System.out.println("Welcome.........");

return new ModelAndView("gagandeep", "message", message);

}

Spring MVC Hello World

2016-06-21T07:05:00.003-04:00

Spring MVC HelloWorld Example

a) Libraries required:

spring-context - 4.1.6
spring-aop - 4.1.6
spring-webmvc - 4.1.6
spring-web 4.1.6
jstl - 1.2

b) Create web.xml file in WEB-INF folder and write following lines of code:

<!DOCTYPE web-app PUBLIC
"-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
<display-name>Archetype Created Web Application</display-name>
<servlet>
<servlet-name>spring</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>spring</servlet-name>
<url-pattern>*.html</url-pattern>
</servlet-mapping>
</web-app>

c) Create a xml file named as spring-servlet.xml inside WEB-INF folder and write following lines of code:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
xmlns:context="http://www.springframework.org/schema/context"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-3.0.xsd">
<context:component-scan base-package="com.gag.controller" />
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/WEB-INF/jsp/" />
<property name="suffix" value=".jsp" />
</bean>
</beans>

d) Create a package named as com.gag.controller (or any other name) and inside this package Create a new class named as HelloWorldController and write following code:

package com.gag.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class HelloWorldController {

@RequestMapping("/hello")
public ModelAndView helloWorld() {
String message = "HELLO SPRING MVC HOW R U";
System.out.println("Here.............");
return new ModelAndView("hellopage", "message", message);
}
}

e) Create a folder inside WEB-INF named as jsp and inside this folder Create a new JSP named as hellopage.jsp and write following code in it:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@page isELIgnored="false" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>${message}
</body>
</html>

Servlet Question Answers

2013-04-23T04:39:00.000-04:00

Certain Servlets interview Q/As

Q1. What is a servlet ?

Servlets are modules that extend request/response-oriented servers,such as Java-enabled web servers. For example, a servlet might be responsible for taking data in an HTML order-entry form and applying the business logic used to update a company’s order database. Servlets are to servers what applets are to browsers. Unlike applets, however, servlets have no graphical user interface.

Q2. Whats the advantages using servlets over using CGI?
Servlets provide a way to generate dynamic documents that is both easier to write and faster to run. Servlets also address the problem of doing server-side programming with platform-specific APIs: they are developed with the Java Servlet API, a standard Java extension.

Q3. What are the general advantages and selling points of Servlets?
A servlet can handle multiple requests concurrently, and synchronize requests. This allows servlets to support systems such as online real-time conferencing. Servlets can forward requests to other servers and servlets. Thus servlets can be used to balance load among several servers that mirror the same content, and to partition a single logical service over several servers, according to task type or organizational boundaries.

Q4. Which package provides interfaces and classes for writing servlets?
javax

Q5. What’s the Servlet Interface?
The central abstraction in the Servlet API is the Servlet interface. All servlets implement this interface, either directly or, more commonly, by extending a class that implements it such as HttpServlet.Servlets > Generic Servlet > HttpServlet > MyServlet. The Servlet interface declares, but does not implement, methods that manage the servlet and its communications with clients. Servlet writers provide some or all of these methods when developing a servlet.

Q6. When a servlet accepts a call from a client, it receives two objects. What are they?
ServletRequest (which encapsulates the communication from the client to the server) and ServletResponse (which encapsulates the communication from the servlet back to the client). ServletRequest and ServletResponse are interfaces defined inside javax.servlet package.

Q7. What information does ServletRequest allow access to?
Information such as the names of the parameters passed in by the client, the protocol (scheme) being used by the client, and the names of the remote host that made the request and the server that received it. Also the input stream, as ServletInputStream.Servlets use the input stream to get data from clients that use application protocols such as the HTTP POST and GET methods.

Q8. What type of constraints can ServletResponse interface set on the client?
It can set the content length and MIME type of the reply. It also provides an output stream, ServletOutputStream and a Writer through which the servlet can send the reply data.

Q9. Explain servlet lifecycle?
Each servlet has the same life cycle: first, the server loads and initializes the servlet (init()), then the servlet handles zero or more client requests (service()), after that the server removes the servlet (destroy()). Worth noting that the last step on some servers is done when they shut down.

Q10. How does HTTP Servlet handle client requests?
An HTTP Servlet handles client requests through its service method. The service method supports standard HTTP client requests by dispatching each request to a method designed to handle that request.

JSP Interview Questions

2013-04-22T20:40:00.002-04:00

Certain JSP interview question answers...

Q1. What is a JSP and what is it used for?

Java Server Pages (JSP) is a platform independent presentation layer technology that comes with SUN s J2EE platform. JSPs are normal HTML pages with Java code pieces embedded in them. JSP pages are saved to *.jsp files. A JSP compiler is used in the background to generate a Servlet from the JSP page.

Q2. What is difference between custom JSP tags and beans?

Custom JSP tag is a tag you defined. You define how a tag, its attributes and its body are interpreted, and then group your tags into collections called tag libraries that can be used in any number of JSP files.

To use custom JSP tags, you need to define three separate components:

1. the tag handler class that defines the tag\'s behavior

2. the tag library descriptor file that maps the XML element names to the tag implementations

3. the JSP file that uses the tag library

When the first two components are done, you can use the tag by using taglib directive:

<%@ taglib uri="xxx.tld" prefix="..." %>

Then you are ready to use the tags you defined.

Let's say the tag prefix is test:

MyJSPTag or JavaBeans are Java utility classes you defined. Beans have a standard format for Java classes. You use tags to declare a bean and use to set value of the bean class and use to get value of the bean class.

<%=identifier.getclassField() %>

Custom tags and beans accomplish the same goals, encapsulating complex behavior into simple and accessible forms.

There are several differences:

a) Custom tags can manipulate JSP content; beans cannot.

b) Complex operations can be reduced to a significantly simpler form with custom tags than with beans. c) Custom tags require quite a bit more work to set up than do beans.

d) Custom tags usually define relatively self-contained behavior, whereas beans are often defined in one servlet and used in a different servlet or JSP page.

e) Custom tags are available only in JSP 1.1 and later, but beans can be used in all JSP 1.x versions.

Q3. What are the two kinds of comments in JSP and what's the difference between them ?

1. JSP Comment

Example: <%-- JSP Comment --%>

2. HTML Comment

Example:

Q4. What is JSP technology?

Java Server Page is a standard Java extension that is defined on top of the servlet Extensions. The goal of JSP is the simplified creation and management of dynamic Web pages. JSPs are secure, platform-independent, and best of all, make use of Java as a server-side scripting language.

Q5. How can a servlet refresh automatically if some new data has entered the database?

You can use a client-side Refresh or Server Push.

Q6. How many JSP scripting elements and what are they?

There are three scripting language elements:

1. declarations

2. scriptlets

3. expressions

Q7. Why are JSP pages the preferred API for creating a web-based client program?

Because no plug-ins or security policy files are needed on the client systems(applet does). Also, JSP pages enable cleaner and more module application design because they provide a way to separate applications programming from web page design. This means personnel involved in web page design do not need to understand Java programming language syntax to do their jobs.

Q8. Is JSP technology extensible?

YES. JSP technology is extensible through the development of custom actions, or tags, which are encapsulated in tag libraries.

Q9. What are the implicit objects?

Implicit objects are objects that are created by the web container and contain information related to a particular request, page, or application.

They are:

1. request

2. response

3. exception

4. pageContext

5. out

6. session

7. application

8. config

9. page

Q10. Can we use the constructor, instead of init(), to initialize servlet?

Yes , of course you can use the constructor instead of init(). There’s nothing to stop you. But you shouldn’t. The original reason for init() was that ancient versions of Java couldn’t dynamically invoke constructors with arguments, so there was no way to give the constructur a ServletConfig. That no longer applies, but servlet containers still will only call your no-arg constructor. So you won’t have access to a ServletConfig or ServletContext.

Q11. What is JSP page?

A JSP page is a text-based document that contains two types of text: static template data, which can be expressed in any text-based format such as HTML, SVG, WML, and XML, and JSP elements, which construct dynamic content.

Java Today: Servlets

2013-01-20T22:42:00.001-05:00

Java Today: Servlets: Basic Information about Servlets in Java: 1. Servlets are server side components that provide a powerful mechanism...

Interview Questions - Servlets and latest version

2013-01-20T09:55:00.001-05:00

Hi Friends...!!..

Check out the new version of Java7. You may click the link below

http://www.java.com/en/download/index.jsp

Some brief information about Java:

1. Java is a general-purpose, concurrent, class-based, object-oriented computer programming language that is specifically designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" meaning that code that runs on one platform does not need to be recompiled to run on another.

2. Java applications are typically compiled to bytecode (class file) that can run on any JVM regardless of computer architecture. Java is, as of 2012, one of the most popular programming languages in use, particularly for client-server web applications, with a reported 15 million users. Java was originally developed by James Gosling at Sun Microsystems (which has since merged into Oracle Corporation) and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C++, but it has fewer low-level facilities than either of them.

Some questions about Servlets:

Technical Interviewers ask mostly from this topic just to check your basic skills.

Q:	What is the difference between HttpServlet and GenericServlet?
A:	A GenericServlet has a service() method aimed to handle requests. HttpServlet extends GenericServlet and adds support for doGet(), doPost(), doHead() methods (HTTP 1.0) plus doPut(), doOptions(), doDelete(), doTrace() methods (HTTP). Both these classes are abstract.

Q:	What is the difference between ServletContext and ServletConfig?
A:	ServletContext: Defines a set of methods that a servlet uses to communicate with its servlet container, for example, to get the MIME type of a file, dispatch requests, or write to a log file. The ServletContext object is contained within the ServletConfig object, which the Web server provides the servlet when the servlet is initialized ServletConfig: The object created after a servlet is instantiated and its default constructor is read. It is created to pass initialization information to the servlet.

sleep() method in Java...

2012-07-16T13:11:00.000-04:00

sleep() method in Java...

1. see which exception it throws

2. see how it works..

Thread.sleep causes the current thread to suspend execution for a specified period. This is an efficient means of making processor time available to the other threads of an application or other applications that might be running on a computer system. The sleep method can also be used for pacing, as shown in the example that follows, and waiting for another thread with duties that are understood to have time requirements, as with the SimpleThreads example in a later section.

Two overloaded versions of sleep are provided: one that specifies the sleep time to the millisecond and one that specifies the sleep time to the nanosecond. However, these sleep times are not guaranteed to be precise, because they are limited by the facilities provided by the underlying OS. Also, the sleep period can be terminated by interrupts, as we'll see in a later section. In any case, you cannot assume that invoking sleep will suspend the thread for precisely the time period specified.

The SleepMessages example uses sleep to print messages at four-second intervals:

public class SleepMessages {
    public static void main(String args[])
        throws InterruptedException {
        String importantInfo[] = {
            "Mares eat oats",
            "Does eat oats",
            "Little lambs eat ivy",
            "A kid will eat ivy too"
        };

        for (int i = 0;
             i < importantInfo.length;
             i++) {
            //Pause for 4 seconds
            Thread.sleep(4000);
            //Print a message
            System.out.println(importantInfo[i]);
        }
    }
}

Notice that main declares that it throws InterruptedException. This is an exception that sleep throws when another thread interrupts the current thread while sleep is active. Since this application has not defined another thread to cause the interrupt, it doesn't bother to catch InterruptedException.

Exceptions in java with an example

2012-07-14T06:47:00.003-04:00

Overview

Java has a powerful concept for exception and error handling. An exception is an error that occurs at runtime. It is either generated by the Java Virtual Machine (VM) in response to an unexpected condition or it is generated by your code as a result of executing a throw statement.

Understanding Exceptions

Exceptions generated from runtime are called unchecked exceptions, since it is not possible for the compiler to determine that your code will handle the exception. Exception classes that descend from RuntimeException and Error classes are unchecked exceptions. Examples for RuntimeException are illegal cast operation, inappropriate use of a null pointer, referencing an out of bounds array element. Errorexception classes signal critical problems that typically cannot be handled by your application. Examples are out of memory error, stack overflow, failure of the Java VM.

Thrown exceptions are referred to as checked exceptions. The compiler will confirm at compile time that the method includes code that might throw an exception. Moreover the compiler requires the code that calls such a method to include this call within atry block, and provide an appropriate catch block to catch the exception.

java.lang.Object
   |
   +--java.lang.Throwable
         |
         +--java.lang.Exception
         |     |
         |     +--java.lang.ClassNotFoundException
         |     |
         |     +--java.io.IOException
         |     |     |
         |     |     +--java.io.FileNotFoundException
         |     |
         |     +--java.lang.RuntimeException
         |           |
         |           +--java.lang.NullPointerException
         |           |
         |           +--java.lang.IndexOutOfBoundsException
         |                 |
         |                 +--java.lang.ArrayIndexOutOfBoundsException
         |
         +--java.lang.Error
               |
               +--java.lang.VirtualMachineError
                     |
                     +--java.lang.OutOfMemoryError

When an (either checked or unchecked) exception is thrown, execution will attempt to immediately branch to the first catch block whose associated exception class matches the class or a superclass of the thrown exception. If the exception does not occur within a try block or the thrown exception is not caught in a matching catchblock, execution of the method immediately terminates and control returns to the invoker of the method, where this process is repeated. The result is that the exception chain is escalated until a matching catch block is found. If not, the thread containing the thrown exception is terminated.

The following Demo1 class demonstrates the behaviour of exceptions and applications.

import java.io.*;

class Demo1 {

public static FileInputStream f1(String fileName)
    throws FileNotFoundException
{
    FileInputStream fis = new FileInputStream(fileName);
    System.out.println("f1: File input stream created");
    return fis;
}

public static FileInputStream f2(String fileName)
{
    FileInputStream fis = null;
    try
    {
      fis = new FileInputStream(fileName);
    }
    catch (FileNotFoundException ex)
    {
      System.out.println("f2: Oops, FileNotFoundException caught");
    }
    finally
    {
      System.out.println("f2: finally block");
    }
    System.out.println("f2: Returning from f2");
    return fis;
}

public static void main(String args[])
{
    FileInputStream fis1 = null;
    FileInputStream fis2 = null;
    String fileName = "foo.bar";
    // String fileName = null;

System.out.println( "main: Starting " + Demo1.class.getName()
+ " with file name = " + fileName);

    // get file input stream 1
    try {
      fis1 = f1(fileName);
    }
    catch (FileNotFoundException ex)
    {
      System.out.println("main: Oops, FileNotFoundException caught");
    }
    catch (Exception ex)
    {
      System.out.println("main: Oops, genreal exception caught");
    }

// get file input stream 2
fis2 = f2(fileName);

System.out.println("main: " + Demo1.class.getName() + " ended");
}
}

Compile and run the Demo1 class will generate output as follows (assuming that the file foo.bar does not exist):

main: Starting Demo1 with file name = foo.bar
main: Oops, FileNotFoundException caught
f2: Oops, FileNotFoundException caught
f2: finally block
f2: Returning from f2
main: Demo1 ended

The example program tries to create two file input streams. Therefore two methods f1and f2 are implemented. First, the main program calls f1 method. Because the constructor of the FileInputStream throws a FileNotFoundException the method f1must be defined with the throws FileNotFoundException in the method definition. The thrown exception is not handled in the method but forwarded to the invoker. Note, that the system output before the return statement is never executed.

So the invoker, in our example the main program, must catch this exception. The method f1 is called in a try block. The following catch blocks catch either aFileNotFoundException or a general Exception. In our example, the exception is caught in the first catch block and the system output is generated. Since the exception in f1 is caught and handled, the execution of the program is not terminated.

Second, the example program creates another FileInputStream invoking the f2method. This method catches the FileNotFoundException, so this exception must not be forwarded to the invoker. The try ... catch statement is followed by a finallyblock. This block is always executed, regardless whether or not an exception occurs within the try block. This generates the system output in our example. Again, the exception is caught and the program executes, this generates the system output inf2 and main.

This was a straight forward example with caught exceptions. What happens with uncaught exceptions? Change the fileName assignment in the main method: Comment out the first assignment and activate the second String fileName = null; then compile and execute Demo1 again. The generated output is:

main: Starting Demo1 with file name = null
main: Oops, genreal exception caught
f2: finally block
java.lang.NullPointerException
java.io.FileInputStream Demo1.f2(java.lang.String)
void Demo1.main(java.lang.String[])
Exception in thread main

This time, we try to create two FileInputStream objects using null instead of a file name. Invoking f1 will generate a NullPointerException which is caught in the main program. Next f2 is called which could handle only the FileNotFoundException but not a NullPointerException. Nevertheless the finally block is executed and then the control returns to the main program. Because there is no try ... catch statement around the call to f2 and no matching catch block is found, the thread is terminated. Note, that f2 and main can not execute the system output statements any more.

How to Track Changes in a Word 2007 Document For Dummies

2012-04-19T08:28:00.000-04:00

How to Track Changes in a Word 2007 Document For Dummies

Hey People..!!.. this feature will help you when you are preparing for requirements for your project in a team of 3 or 4 as it will track the changes made by the particular user.

Implementing an equals() Method

2012-04-14T03:01:00.000-04:00

Overriding equals()

You learned about the equals() method in earlier chapters, where we looked at the wrapper classes. We discussed how comparing two object references using the == operator evaluates to true only when both references refer to the same object (because == simply looks at the bits in the variable, and they're either identical or they're not). You saw that the String class and the wrapper classes have overridden the equals() method (inherited from class Object), so that you could compare two different objects (of the same type) to see if their contents are meaningfully equivalent. If two different Integer instances both hold the int value 5, as far as you're concerned they are equal. The fact that the value 5 lives in two separate objects doesn't matter.
When you really need to know if two references are identical, use ==. But when you need to know if the objects themselves (not the references) are equal, use the equals() method. For each class you write, you must decide if it makes sense to consider two different instances equal. For some classes, you might decide that two objects can never be equal. For example, imagine a class Car that has instance variables for things like make, model, year, configuration—you certainly don't want your car suddenly to be treated as the very same car as someone with a car that has identical attributes. Your car is your car and you don't want your neighbor Billy driving off in it just because, "hey, it's really the same car; the equals() method said so." So no two cars should ever be considered exactly equal. If two references refer to one car, then you know that both are talking about one car, not two cars that have the same attributes. So in the case of a Car you might not ever need, or want, to override the equals() method. Of course, you know that isn't the end of the story.

Implementing an equals() Method

public class EqualsTest {
public static void main (String [] args) {
Moof one = new Moof(8);
Moof two = new Moof(8);
if (one.equals(two)) {
System.out.println("one and two are equal");
}
}
}
class Moof {
private int moofValue;
Moof(int val) {
moofValue = val;
}
public int getMoofValue() {
return moofValue;
}
public boolean equals(Object o) {
if ((o instanceof Moof) && (((Moof)o).getMoofValue()
== this.moofValue)) {
return true;
} else {
return false;
}
}
}

How to convert a date String to a Date or Calendar object?

2012-04-10T11:04:00.001-04:00

How to convert a date String to a Date or Calendar object?

DateFormat formatter = new SimpleDateFormat("MM/dd/yy");
Date date = formatter.parse("01/29/02");

See SimpleDateFormat javadoc for more.And to turn it into a Calendar, do:

Calendar calendar = Calendar.getInstance();
calendar.setTime(date);

Sample Program:


import java.util.*;
import java.text.*;
public class DateToCalender {
public static void main(String[] args) {
 try {  String str_date="11-June-07";
  DateFormat formatter ; 
  Date date ; 
  formatter = new SimpleDateFormat("dd-MMM-yy");
  date = (Date)formatter.parse(str_date); 
 Calendar cal=Calendar.getInstance();
 cal.setTime(date);
 System.out.println("Today is " +cal );
  }
  catch (ParseException e)
  {System.out.println("Exception :"+e);  }  
 
 }
}

OCJP Preparation Questions and Answers (New Q/As Added)

2012-04-07T07:48:00.000-04:00

OCJP Preparation

What is the output for the below code ?

Question 1.

public class A {
int add(int i, int j) {
return i + j;
}
}

public class B extends A {
public static void main(String argv[]) {
short s = 9;
System.out.println(add(s, 6));
}
}

Options are:

A. Compile fail due to error on line no 2

B. Compile fail due to error on line no 9

C. Compile fail due to error on line no 8

D. 15

Answer :

B is the correct answer.

Cannot make a static reference to the non-static method add(int, int) from the type A. The short s is autoboxed correctly, but the add() method cannot be invoked from a static method because add() method is not static.

Question 2.

public class A {
int k;
boolean istrue;
static int p;

public void printValue() {
System.out.print(k);
System.out.print(istrue);
System.out.print(p);
}
}

public class Test {
public static void main(String argv[]) {
A a = new A();
a.printValue();
}
}

Options are:

A.0 false 0

B.0 true 0

C.0 0 0

D.Compile error – static variable must be initialized before use.

Answer :

A is the correct answer.

Global and static variable need not be initialized before use. Default value of global and static int variable is zero. Default value of boolean variable is false. Remember local variable must be initialized before use.

Question 3.

public class Test {
int _$;
int $7;
int do;

public static void main(String argv[]) {
Test test = new Test();
test.$7 = 7;
test.do = 9;
System.out.println(test.$7);
System.out.println(test.do);
System.out.println(test._$);
}
}

Options are:

A.7 9 0

B.7 0 0

C.Compile error – $7 is not valid identifier.

D.Compile error – do is not valid identifier.

Answer:

D is the correct answer. $7 is valid identifier. Identifiers must start with a letter, a currency character ($), or underscore ( _ ). Identifiers cannot start with a number. You can’t use a Java keyword as an identifier. do is a Java keyword.

Question 4.

package com;

class Animal {
public void printName() {
System.out.println("Animal");
}
}

package exam;

import com.Animal;

public class Cat extends Animal {
public void printName() {
System.out.println("Cat");
}
}

package exam;

import com.Animal;

public class Test {
public static void main(String[] args) {
Animal a = new Cat();
a.printName();
}
}

Options are:

A.Animal

B.Cat

C.Animal Cat

D.Compile Error

Answer :

D is the correct answer.

Cat class won’t compile because its superclass, Animal, has default access and is in a different package. Only public superclass can be accessible for different package.

Question 5.

public class A {
int i = 10;

public void printValue() {
System.out.println("Value-A");
}
}

public class B extends A {
int i = 12;

public void printValue() {
System.out.print("Value-B");
}
}

public class Test {
public static void main(String argv[]) {
A a = new B();
a.printValue();
System.out.println(a.i);
}
}

Options are:

A.Value-B 11

B.Value-B 10

C.Value-A 10

D.Value-A 11

Answer:

B is the correct answer.

If you create object of subclass with reference of super class like ( A a = new B();) then subclass method and super class variable will be executed.

Question 6.

public enum Test {
BREAKFAST(7, 30), LUNCH(12, 15), DINNER(19, 45);
private int hh;
private int mm;

Test(int hh, int mm) {
assert (hh >= 0 && hh <= 23) : "Illegal hour.";
assert (mm >= 0 && mm <= 59) : "Illegal mins.";
this.hh = hh;
this.mm = mm;
}

public int getHour() {
return hh;
}

public int getMins() {
return mm;
}

public static void main(String args[]){
Test t = new BREAKFAST;
System.out.println(t.getHour() +":"+t.getMins());
}
}

Options are:

A.7:30

B.Compile Error – an enum cannot be instantiated using the new operator.

C.12:30

D.19:45

Answer:

B is the correct answer.

As an enum cannot be instantiated using the new operator, the constructors cannot be called explicitly. You have to do like Test t = BREAKFAST;

Question 7.

public class A {
static {
System.out.println("static:");
}
{
System.out.println("block");
}

public A() {
System.out.println("A");
}

public static void main(String[] args) {
A a = new A();
}
}

Options are:

A.A block static

B.static block A

C.static A

D.A

Answer:

B is the correct answer.

First execute static block, then statement block then constructor.

Question 8.

public class Test {
public static void main(String[] args) {
int i = 010;
int j = 07;
System.out.println(i);
System.out.println(j);
}
}

Options are:

A.8 7

B.10 7

C.Compilation fails with an error at line 3

D.Compilation fails with an error at line 5

Answer:

A is the correct answer.

By placing a zero in front of the number is an integer in octal form. 010 is in octal form .so its value is 8.

Question 9.

public class Test {
public static void main(String[] args) {
byte b = 6;
b += 8;
System.out.println(b);
b = b + 7;
System.out.println(b);
}
}

Options are:

A.14 21

B.14 13

C.Compilation fails with an error at line 6

D.Compilation fails with an error at line 4

Answer:

C is the correct answer.

int or smaller expressions always resulting in an int. So compiler complain about Type

mismatch: cannot convert from int to byte for b = b+7; But b += 7; // No problem

because +=, -=, *=, and /= will all put in an implicit cast. b += 7 is same as b = (byte)b+7

so compiler not complain.

Question 10.

public class Test {
public static void main(String[] args) {
String value = "abc";
changeValue(value);
System.out.println(value);
}

public static void changeValue(String a) {
a = "xyz";
}
}

Options are:

A.abc

B.xyz

C.Compilation fails

D.Compilation clean but no output

Answer:

A is the correct answer.

Java pass reference as value. passing the object reference, and not the actual object itself.

Simply reassigning to the parameter used to pass the value into the method will do

nothing, because the parameter is essentially a local variable.

Question 11.

public class Test {
public static void printValue(int i, int j, int k) {
System.out.println("int");
}

public static void printValue(byte... b) {
System.out.println("long");
}

public static void main(String... args) {
byte b = 9;
printValue(b, b, b);
}
}

Options are:

A.long

B.int

C.Compilation fails

D.Compilation clean but throws RuntimeException

Answer:

B is the correct answer.

Primitive widening uses the smallest method argument possible. (For Example if you pass short value to a method but method with short argument is not available then compiler choose method with int argument). But in this case compiler will prefer the older style before it chooses the newer style, to keep existing code more robust. var-args method is looser than widen.

Question 12.

You have a java file name Test.java inside src folder of javaproject directory. You have also classes
folder inside javaproject directory. you have issued below command from command prompt.

cd javaproject

Which of the below command puts Test.class file inside classes folder ?

Options are:

A.javac -d classes src/Test.java

B.javac Test.java

C.javac src/Test.java

D.javac classes src/Test.java

Answer:

A is the correct answer.

The -d option lets you tell the compiler in which directory to put the .class file it

generates (d for destination)

Question 13.

You have two class files name Test.class and Test1.class inside javaproject directory.

Test.java source code is :

public class Test {
public static void main(String[] args) {
System.out.println("Hello Test");
}
}

Test1.java source code is :

public class Test1 {
public static void main(String[] args) {
System.out.println("Hello Test1");
}
}

you have issued below commands from command prompt.

cd javaproject

java Test Test1

What is the output ?

Options are:

A.Hello Test

B.Hello Test Hello Test1

C.Hello Test1

D.Run fails – class not found

Answer:

A is the correct answer.

You must specify exactly one class file to execute. If more than one then first one will be executed.

Question 14.

You have a java file name Test.java .

Test.java needs access to a class contained in app.jar in “exam”

directory.

Which of the following command set classpath to compile clean?

Options are:

A.javac -classpath exam/app.jar Test.java

B.javac -classpath app.jar Test.java

C.javac -classpath exam Test.java

D.None of the above

Answer:

A is the correct answer.

javac -classpath exam/app.jar Test.java is the correct command to set exam/app.jar in classpath.

Question 15.

What will be the result of compiling the following code:

public class SuperClass {
public int doIt(String str, Integer... data) throws Exception {
String signature = "(String, Integer[])";
System.out.println(str + " " + signature);
return 1;
}
}

public class SubClass extends SuperClass {
public int doIt(String str, Integer... data) {
String signature = "(String, Integer[])";
System.out.println("Overridden: " + str + " " + signature);
return 0;
}

public static void main(String... args) {
SuperClass sb = new SubClass();
sb.doIt("hello", 3);
}
}

Options are:

A.Overridden: hello (String, Integer[])

B.hello (String, Integer[])

C.Complilation fails

D.None of the above

Answer:

C is the correct answer.

Unhandled exception type Exception.

Question 16:

What will be the result of following code:

class MyException1 extends Exception {
public MyException1() {
}
}

class MyException2 extends Exception {
public MyException2() {
}
}

class ExceptionTest {
public static void main(String[] args) throws Exception {
try {
m2();
} finally {
m3();
} catch (MyException2 e) {
}

}

public static void m2() throws MyException1 {
throw new MyException1();
}

public static void m3() throws MyException2 {
throw new MyException2();
}
}

Options:

A. It will compile but will throw MyException1 when run.

B. It will compile but will throw MyException2 when run.

C. It will compile and run without throwing any exceptions.

D. It will not compile.

Answer: D

Explaination : catch block will come after try block

Errors in Jasper Report

2012-03-22T23:33:00.001-04:00

Errors in Jasper Reports:-

net.sf.jasperreports.engine.JRException: Errors were encountered when compiling report expressions class file:
1. Only a type can be imported. it.businesslogic.ireport.IReportScriptlet resolves to a package
import it.businesslogic.ireport.IReportScriptlet;
<--------------------------------------->
1 errors

Solution :- remove this line from the report(.jrxml) as shown below..This might come in ireport version 2.0.1 and when your ate using jasper jar 3.1.2

Jasper Reports Video

2012-03-10T08:44:00.000-05:00

In Java
This is a small help for all those people who are adding jasper reports as a feature in their project. This basically helps us to generate reports in the form of .PDF and in the excel form also.

Garbage Collection in Java

2012-03-09T11:12:00.000-05:00

Garbage Collection in Java

Overview of Memory Management and Garbage Collection

Memory management is a crucial element in many types of applications. Consider a program that reads in large amounts of data, say from somewhere else on a network, and then writes that data into a database on a hard drive. A typical design would be to read the data into some sort of collection in memory, perform some operations on the data, and then write the data into the database. After the data is written into the database, the collection that stored the data temporarily must be emptied of old data or deleted and recreated before processing the next batch. This operation might be performed thousands of times, and in languages like C or C++ that do not offer automatic garbage collection, a small flaw in the logic that manually empties or deletes the collection data structures can allow small amounts of memory to be improperly reclaimed or lost. Forever. These small losses are called memory leaks, and over many thousands of iterations they can make enough memory inaccessible that programs will eventually crash. Creating code that performs manual memory management cleanly and thoroughly is a nontrivial and complex task, and while estimates vary, it is arguable that manual memory management can double the development effort for a complex program. Java's garbage collector provides an automatic solution to memory management. In most cases it frees you from having to add any memory management logic to your application. The downside to automatic garbage collection is that you can't completely control when it runs and when it doesn't.

Overview of Java's Garbage Collector

Let's look at what we mean when we talk about garbage collection in the land of Java. From the 30,000 ft. level, garbage collection is the phrase used to describe automatic memory management in Java. Whenever a software program executes (in Java, C, C++, Lisp, Ruby, and so on), it uses memory in several different ways. We're not going to get into Computer Science 101 here, but it's typical for memory to be used to create a stack, a heap, in Java's case constant pools, and method areas. The heap is that part of memory where Java objects live, and it's the one and only part of

memory that is in any way involved in the garbage collection process. A heap is a heap is a heap. For the exam it's important to know that you can call it the heap, you can call it the garbage collectible heap, or you can call it Johnson, but there is one and only one heap. So, all of garbage collection revolves around making sure that the heap has as much free space as possible. For the purpose of the exam, what this boils down to is deleting any objects that are no longer reachable by the Java program running. We'll talk more about what reachable means, but let's drill this point in. When the garbage collector runs, its purpose is to find and delete objects that cannot be reached. If you think of a Java program as being in a constant cycle of creating the objects it needs (which occupy space on the heap), and then discarding them when they're no longer needed, creating new objects, discarding them, and so on, the missing piece of the puzzle is the garbage collector. When it runs, it looks for those discarded objects and deletes them from memory so that the cycle of using memory and releasing it can continue. Ah, the great circle of life.

When Does the Garbage Collector Run?

The garbage collector is under the control of the JVM. The JVM decides when to run the garbage collector. From within your Java program you can ask the JVM to run the garbage collector, but there are no guarantees, under any circumstances, that the JVM will comply. Left to its own devices, the JVM will typically run the garbage collector when it senses that memory is running low. Experience indicates that when your Java program makes a request for garbage collection, the JVM will usually grant your request in short order, but there are no guarantees. Just when you think you can count on it, the JVM will decide to ignore your request.

How Does the Garbage Collector Work?

You just can't be sure. You might hear that the garbage collector uses a mark and sweep algorithm, and for any given Java implementation that might be true, but the Java specification doesn't guarantee any particular implementation. You might hear

that the garbage collector uses reference counting; once again maybe yes maybe no. The important concept to understand for the exam is when does an object become eligible for garbage collection? To answer this question fully, we have to jump ahead

a little bit and talk about threads. (See Chapter 9 for the real scoop on threads.) In a nutshell, every Java program has from one to many threads. Each thread has its own little execution stack. Normally, you (the programmer) cause at least one thread to run in a Java program, the one with the main() method at the bottom of the stack. However, as you'll learn in excruciating detail in Chapter 9, there are many really cool reasons to launch additional threads from your initial thread. In addition to having its own little execution stack, each thread has its own lifecycle. For now, all we need to know is that threads can be alive or dead. With this background information, we can now say with stunning clarity and resolve that an object is eligible for garbage collection when no live thread can access it. (Note: Due to the vagaries of the String constant pool, the exam focuses its garbage collection questions on non-String objects, and so our garbage collection discussions apply to only non-String objects too.) Based on that definition, the garbage collector does some magical, unknown operations, and when it discovers an object that can't be reached by any live thread,

it will consider that object as eligible for deletion, and it might even delete it at some point. (You guessed it; it also might not ever delete it.) When we talk about reaching an object, we're really talking about having a reachable reference variable that refers to the object in question. If our Java program has a reference variable

that refers to an object, and that reference variable is available to a live thread, then that object is considered reachable. We'll talk more about how objects can become unreachable in the following section. Can a Java application run out of memory? Yes. The garbage collection system attempts to remove objects from memory when they are not used. However, if you maintain too many live objects (objects referenced from other live objects), the system can run out of memory. Garbage collection cannot ensure that there

is enough memory, only that the memory that is available will be managed as efficiently as possible.

2012-03-05T03:46:00.002-05:00

This is basically for all those hard-core coders so that they sit properly before the laptop and their neck doesn't pain..!!!...please follow it..!!

Boxing and Unboxing in Java

2012-03-04T14:12:00.000-05:00

Boxing and Unboxing in Java

Boxing and Unboxing make using wrapper classes more convenient.
In Java 5, new feature came, and it was Auto-boxing and Auto-unboxing.
In the old, pre-Java 5 days, if you wanted to make a wrapper, unwrap it, use it, and then rewrap it, you might do something like this:

Integer y = new Integer(56); // make it
int x= y.intValue(); // unwrap it
x++; // use it
y = new Integer(x); // re-wrap it
System.out.println("y =" + y); // print it

Now improved version of Java 5 you can say,

Integer y = new Integer(56); //make it
y++; //unwrap-it, increment-it, rewrap-it
System.out.println("y = " + y); // print it

Both Examples produce the output::

y=57

Behind the scenes, the compiler does the unboxing and reassignment for you.
We knew that wrapper objects are immutable, this example appears to contradict that statement. It sure looks like y's value changes fro 56 to 57.
What actually happened, is that second wrapper object was created and its value was set to 57.
We could only prove it as:-

Integer y = 56; // make a wrapper
Integer x = y; // assign a second ref var to the wrapper

System.out.println(y==x);
y++; //unwrap, use , rewrap
System.out.println(x+ " " + y); // print values

System.out.println(y==x); //verify that they refer
// to different objects

Which produces the output:

true
56 57
false

So under the covers when the compiler got to the line y++; it had to substitute something like this:

int x2 = y.intValue(); // unwrap it
x2++;
y = new Integer(x2); // rewrap-it

Where Boxing Can Be Used

It is very common to use wrappers in conjunction with collections.
Any time you want your collection to hold objects and primitives, you 'll want to us wrappers to make those primitives collection-compatible.
The general rule is that boxing and unboxing work wherever you can normally use a primitive or a wrapped object.

class UseBoxing {
public static void main(String args[])
{
UseBoxing u = new UseBoxing();
u.go(5);
}
boolean go(Integer i)
{
Boolean ifSo = true; //boxes the int
Short s = 400; //boxes the literal
if(ifSo)
{ // unboxing
System.out.println(++s); //unboxes, increments,
// reboxes.
}
return !ifSo;
}
}

2012-01-16T12:48:00.000-05:00

Vector Class in J2SE

It extends AbstractList, which is also a class in java.

It implements List, RandomAccess, Cloneable, Serializable, these are interfaces in java.

Like an array, it contains components that can be accessed using an integer index. However, the size of vector can grow or shrink as needed to accomodate adding and removing items after the vector has been created.

Each Vector tries to optimize storage management by maintaining a capacity and a capacityIncrement.

Vector Size <= Capacity.

Java Today

Software Support & Development for Students, Shops and Companies

Spring and RESTful webservice Integration

RESTful webservice along with Spring 4 and AngularJS

RESTful WebService using Jersey, AngularJS, MySQL (Small application to maintain users - Usermaintenance)

Spring MVC Multiple Controller Example

Spring MVC Hello World

Servlet Question Answers

JSP Interview Questions

Certain JSP interview question answers...

Java Today: Servlets

Interview Questions - Servlets and latest version

sleep() method in Java...

Exceptions in java with an example

How to Track Changes in a Word 2007 Document For Dummies

How to Track Changes in a Word 2007 Document For Dummies

Implementing an equals() Method

How to convert a date String to a Date or Calendar object?

OCJP Preparation Questions and Answers (***New Q/As Added***)

Question 5.

Question 6.

Question 7.

Question 9.

Question 10.

Question 11.

Question 12.

Question 13.

Question 14.

You have a java file name Test.java .

Question 15.

Errors in Jasper Report

Jasper Reports Video

Garbage Collection in Java

Boxing and Unboxing in Java

OCJP Preparation Questions and Answers (New Q/As Added)